1. Field of the Invention
The present invention relates to an ink jet printer, and, more particularly, to firing nozzles in an ink jet printer.
2. Description of the Related Art
An ink jet printer typically includes an ink jet printhead assembly having a nozzle plate which is mounted in spaced apart relationship to a printhead. The nozzle plate includes a plurality of ink emitting orifices which are respectively disposed in association with a plurality of heater elements mounted on the printhead. When a particular heater element is actuated or fired, ink disposed adjacent thereto rapidly expands to form a vapor bubble. Ink is expelled through the orifice by the bubble and is jetted onto the print medium.
It is known to improve print quality by applying a short prefire pulse to a heater element in order to raise the temperature of the ink before a fire pulse is applied to the heater element. The fire pulse causes a vapor bubble and jetting of the ink, but the prefire pulse does not. A problem is that the time required to apply the prefire pulse adds to the total printing time and reduces the throughput of the printer. Thus, there is a trade-off between the quality of printing, which benefits from the application of prefire pulses, and the speed of printing, which is decreased by the application of prefire pulses.
It is also known to control the ejection of ink by adjusting, among other factors, the width, i.e., time duration, of driving pulses that are applied to the ink heaters. In general, longer driving pulses result in better print quality. Again, there is a trade-off between the quality of printing, which benefits from longer driving pulses, and printing speed, which benefits from shorter driving pulses.
The speed and print quality of ink jet printers is constantly increasing, although there is an engineering trade-off between these two attributes, as described above. Increasing print speed in many cases implies that there will be a decrease in print quality. This is true because ink bubble formation parameters, which produce better ink drop shapes and thus better print quality, are often compromised to increase print speed. Conversely, an increase in print quality is often achieved at the expense of print speed.
What is needed in the art is a way to either increase print speed without decreasing print quality, or increase print quality without decreasing print speed.